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Sökning: WFRF:(Henn Jonathan)

  • Resultat 1-7 av 7
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1.
  • Halbritter, Aud H., et al. (författare)
  • Plant trait and vegetation data along a 1314 m elevation gradient with fire history in Puna grasslands, Perú
  • 2024
  • Ingår i: SCIENTIFIC DATA. - 2052-4463. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Alpine grassland vegetation supports globally important biodiversity and ecosystems that are increasingly threatened by climate warming and other environmental changes. Trait-based approaches can support understanding of vegetation responses to global change drivers and consequences for ecosystem functioning. In six sites along a 1314 m elevational gradient in Puna grasslands in the Peruvian Andes, we collected datasets on vascular plant composition, plant functional traits, biomass, ecosystem fluxes, and climate data over three years. The data were collected in the wet and dry season and from plots with different fire histories. We selected traits associated with plant resource use, growth, and life history strategies (leaf area, leaf dry/wet mass, leaf thickness, specific leaf area, leaf dry matter content, leaf C, N, P content, C and N isotopes). The trait dataset contains 3,665 plant records from 145 taxa, 54,036 trait measurements (increasing the trait data coverage of the regional flora by 420%) covering 14 traits and 121 plant taxa (ca. 40% of which have no previous publicly available trait data) across 33 families.
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2.
  • Martins, Inês S., et al. (författare)
  • Widespread shifts in body size within populations and assemblages
  • 2023
  • Ingår i: Science. - 0036-8075 .- 1095-9203. ; 381:6662, s. 1067-1071
  • Tidskriftsartikel (refereegranskat)abstract
    • Biotic responses to global change include directional shifts in organismal traits. Body size, an integrative trait that determines demographic rates and ecosystem functions, is thought to be shrinking in the Anthropocene. Here, we assessed the prevalence of body size change in six taxon groups across 5025 assemblage time series spanning 1960 to 2020. Using the Price equation to partition this change into within-species body size versus compositional changes, we detected prevailing decreases in body size through time driven primarily by fish, with more variable patterns in other taxa. We found that change in assemblage composition contributes more to body size changes than within-species trends, but both components show substantial variation in magnitude and direction. The biomass of assemblages remains quite stable as decreases in body size trade off with increases in abundance.
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3.
  • Anderegg, G. C., et al. (författare)
  • Litter removal reduces seed predation in restored prairies during times when seed predation would otherwise be high
  • 2022
  • Ingår i: Restoration Ecology. - : Wiley. - 1061-2971 .- 1526-100X. ; 30:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Understanding patterns of seed predation in tallgrass prairie restorations is vital because seed additions are often used by managers to increase diversity and promote native species. However, the success of seed additions depends on the extent of seed predation. It is not clear how seed predation varies through time and to what extent it is affected by various commonly used management techniques in grasslands (e.g. spring or fall prescribed burns, mowing). We examined how predation of Sorghastrum nutans seeds changed during eight trials between June 2018 and April 2019 in plots that received one of four different plant litter removal treatments (fall mow, fall burn, spring burn, and unaltered control). Granivory varied throughout the year, reaching its peak in the late fall and early winter. However, we found that seed predators consumed significantly fewer seeds when litter was removed following fall burn and fall mow treatment applications. These treatments occurred during times when granivory was otherwise high in areas where litter remained intact (control and spring burn plots). Our findings highlight the importance of management decisions and how they interact with granivory in grassland restorations. Both time of year and litter cover determine seed predation rates; seed predators consume more seeds when seeds are abundant but rely on intact litter cover while foraging. This suggests that if seeds are added during the fall, litter should be removed to minimize the loss of seeds to granivory. Alternatively, seed additions during the spring are likely to experience lower rates of seed predation.
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4.
  • Henn, Jonathan, et al. (författare)
  • Disturbance Type and Timing Affect Growth and Tolerance Strategies in Grassland Plant Leaves
  • 2022
  • Ingår i: Rangeland Ecology and Management. - : Elsevier BV. - 1550-7424. ; 80, s. 18-25
  • Tidskriftsartikel (refereegranskat)abstract
    • As human activities alter winter climates and disturbance regimes in grassland and rangeland ecosystems, the temperatures that plants experience during spring are changing. Litter can help buffer overwintering herbaceous plants from temperature fluctuations, and management practices dictate whether litter is present during the winter. Here, we investigate how disturbance type (burning, mowing) and timing (spring, fall) affect leaf characteristics related to growth and stress tolerance and how these traits change over time for five common tallgrass prairie species including four forb (Monarda fistulosa, Ratibida pinnata, Silphium integrifolium, Symphiotrichum laeve) and one grass species (Bromus inermis). To do this, we established a field experiment in Wisconsin, where plots were annually burned in the fall, mowed in the fall, burned in the spring, or left undisturbed (control) for 3 yr. We sampled leaves of target species seven times from spring emergence through early summer to measure specific leaf area (SLA) and leaf cold tolerance in each treatment. Leaves from fall-burned plots had lower SLAs, while leaves in spring-burned plots had higher SLAs early in the growing season. Leaf cold tolerance was similar across most treatments except in spring-burn plots, where leaves became more cold-hardy through time. We found weak evidence of a tradeoff between leaf growth and both cold tolerance and SLA. These results suggest that management decisions like litter removal before winter (e.g., fall burn or mow) prompted different plant responses compared with plots where litter was present during winter (e.g., spring burn). As species respond to winter climate change, management decisions have implications for mitigating climate change impacts and maintaining diversity in grasslands by affecting early-season plant growth strategies. For example, removing litter in the fall by burning promotes stress-tolerant responses, which may better equip plants to tolerate changing spring conditions.
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5.
  • Henn, Jonathan, et al. (författare)
  • Plant age affects intraspecific variation in functional traits
  • 2021
  • Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 222:6, s. 669-680
  • Tidskriftsartikel (refereegranskat)abstract
    • Functional traits are often used to examine ecological patterns and processes. Ontogeny-changes that occur over time as the result of development-generates variation in traits within individual organisms. We aimed to quantify the role of ontogeny in structuring functional trait variation across a range of co-existing herbaceous perennial species and hypothesized that ontogenetic variation in traits would be greater in younger vs. older plants. We grew eight herbaceous perennial forb species common in tallgrass prairies from seed in a greenhouse in Madison, Wisconsin, USA to determine how and when time-related variation in functional traits is large relative to other sources of variation, such as differences between leaves and species. We destructively measured common functional traits on four individuals of each species every two weeks for 19 weeks, including leaf mass fraction, root mass fraction, stem mass fraction, specific leaf area, leaf dry matter content, and leaf area. We found that most functional traits indeed change through time, that the direction of many changes are consistent between species but the magnitude of change is species specific, and most time-related variation occurred earlier in development. These results emphasize the importance of considering sampling timing and differences between young and old plants when measuring functional traits. Our results suggest that ontogenetic intraspecific variation can be substantial, especially early in life. It may be problematic to use traits measured from mature plants to interpret the importance of processes that occur at earlier life stages or vice versa; using seedling traits to understand adult plant responses may also be inappropriate.
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6.
  • Pastur, G. J. M., et al. (författare)
  • Landscape Variables Influence over Active Restoration Strategies of Nothofagus Forests Degraded by Invasive Castor canadensis in Tierra del Fuego
  • 2021
  • Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 13:14
  • Tidskriftsartikel (refereegranskat)abstract
    • North American beavers (Castor canadensis) are responsible for the major changes in the Tierra del Fuego Archipelago, altering riparian forests for the long-term. Passive restoration of the areas affected was ineffective in the medium-term (up to 20 years), being necessary active strategies. Plantations in abandoned ponds were made with Nothofagus pumilio and N. antarctica tree species across Tierra del Fuego island (Argentina). In the first experiment, we analysed the influence of biotic and abiotic factors in three micro-habitats in the impacted areas: front and tail of ponds, and cut not-flooded forest areas. Five-years-old N. pumilio seedlings had 39% survival in front, 21% in tails, and 46% in cut areas at year-3 of the restoration experiments, being negatively influenced by plant cover and soil moisture. Lower growth was recorded during year-1 (0.7-0.9 cm yr(-1)), but increased on time (1.9 cm yr(-1) front, 1.6 cm yr(-1) tail, 4.3 cm yr(-1) cut areas). A second experiment explores the alternative to substitute the tree species to face the harder conditions of the impact and climate change. For this, we conducted a new plantation at four locations across the main bioclimatic zones, where 10-40 cm N. antarctica plants attained 17% survival in meadows (front and tail) and 30% in cut areas, being higher with larger than smaller plants (25% vs. 18%), and where they are mainly influenced by rainfall (4% in sites 400 mm yr(-1)). The main damage was detected in the above-ground biomass due to dryness, but root survival allowed the emergence of new shoots in the following growing season. It is necessary to monitor different Nothofagus species across natural environments in the landscape to determine the feasibility and effectiveness of different strategies in restoration plans, considering the selection of climate-resilient tree species.
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7.
  • Vandvik, Vigdis, et al. (författare)
  • Plant traits and associated data from a warming experiment, a seabird colony, and along elevation in Svalbard
  • 2023
  • Ingår i: Scientific Data. - 2052-4463. ; 10:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The Arctic is warming at a rate four times the global average, while also being exposed to other global environmental changes, resulting in widespread vegetation and ecosystem change. Integrating functional trait-based approaches with multi-level vegetation, ecosystem, and landscape data enables a holistic understanding of the drivers and consequences of these changes. In two High Arctic study systems near Longyearbyen, Svalbard, a 20-year ITEX warming experiment and elevational gradients with and without nutrient input from nesting seabirds, we collected data on vegetation composition and structure, plant functional traits, ecosystem fluxes, multispectral remote sensing, and microclimate. The dataset contains 1,962 plant records and 16,160 trait measurements from 34 vascular plant taxa, for 9 of which these are the first published trait data. By integrating these comprehensive data, we bridge knowledge gaps and expand trait data coverage, including on intraspecific trait variation. These data can offer insights into ecosystem functioning and provide baselines to assess climate and environmental change impacts. Such knowledge is crucial for effective conservation and management in these vulnerable regions.
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  • Resultat 1-7 av 7

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